Upgrade with minimal downtime
Clouds are expected to be always available and involve large numbers of servers. This blueprint looks how we can perform upgrades with minimal disruption.
Goals for the upgrade are:
- where possible, transparent to the cloud users
- minimal instance downtime or instance connectivity loss
- ability to rollback to a pre-upgrade state if things fail
- ability to upgrade from v2 to v4 without having to do upgrade to v3 first (supporting at least two versions forward/back?)
- define what we mean by v2 and v4. It could mean 2012.1 -> 2012.3 (etc.), but what about sprint releases, what about bug fix releases to major versions (http://
This needs to be broken out into concrete steps and blueprints by the upgrades team --Vish
* Blueprints in grey have been implemented.